A student at Deer Valley High School in Antioch has been diagnosed with tuberculosis, which means much of the student body is now expected to get tested for the disease.
On the school's website, Principal Kenneth Gardner wrote: "Contra Costa Health Services will be at the school doing TB testing on any student who shared a classroom or was in a club with the student with tuberculosis, and we have sent information home to those families."
According to the Contra Costa Times, about 200 students will be tested and the student who contracted the disease is no longer infectious and was back in school Monday.
The risk of advancing from infection to disease is only about 10 percent. Tuberculosis is an airborne bacterial infection of the lungs spread through the air. Symptoms can include a prolonged cough, rapid weight loss, fevers and night sweats.
The principal's letter said: "There is currently no evidence that there are any other cases or tuberculosis disease in the school or that the disease has spread to any other student."
Testing is expected on Thursday.